The present invention relates to an apparatus for operating control surfaces in an aircraft.
Aircrafts are usually equipped with mechanical transmission system or systems for adjusting the position of the several control surfaces. These mechanical signal transmission systems, particularly for example for adjusting the elevators providing correspondingly the elevational control for the aircraft, are preferred but only if in the case of manual control a supplemental utilization of electrical or other control signals are not needed. Also it was found that the mechanical operation of control surfaces is more economical as well as safer than an analogous electrical system.
Independently from the foregoing, electrical signal transmission paths between, utimately, the pilot and the control surfaces have been used in lieu of mechanical control systems. These electrical control systems are known generally or have been designated generally by the term "fly by wire" systems. A fly by wire system is preferred in those cases in which independently developed controlled signals are to be superimposed upon the commands provided by the pilot. For this reason electrical control systems in general including transmission systems of an electrical nature linking the pilot with the control surfaces are deemed to be attractive. Nevertheless, inspite of these advantages, electrical control signals have not been used extensively in commercial aircraft and the reason here is the belief that these electrical control systems are less reliable than mechanical control systems. Of course, the reliability of an electrical control system can be enhanced through redundancy but clearly the concept of redundancy is inherently an uneconomical one.